Oh!!! You just answer to my question about why people never get back to me for this upgrade...I'm feeling stupid.
Of course I talk about squeeze.
So now this is more clear (thanks to you) any tips?
EDIT: now that i'm looking for the right thing ifound this:
Ok i'll try both if it's going to be part of php i'd better to go for apc.
EDIT: got an internal server error(500) when installing apc.
[Wed Nov 30 12:01:25 2011] [notice] mod_fcgid: call /var/www/domain.com/web/wp-admin/admin-ajax.php with wrapper /var/www/php-fcgi-scripts/web44/.php-fcgi-starter
PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php5/20060613/apc.so' - /usr/lib/php5/20060613/apc.so: cannot open shared object file: No such file or directory in Unknown on line 0